Support for structural components and method for producing the same

ABSTRACT

A support for structural components that are subjected to a thermal treatment process. The support includes a frame having limbs and extending therefrom a grid of intersecting strands. In order to prevent the support from warping even when subjected to strong thermal loads or variations in temperature, the frame is produced from a temperature-resistant material and the strands are produced from carbon fibers or ceramic fibers that form the grid, extending from the limbs of the frame.

The invention relates to a carrier for structural parts to be subjectedto a heat-treatment process, including at least one frame and a latticeextending therefrom consisting of intersecting strands, the framecomprising one or more limbs which preferably form a polygon.

To position or fix slim metallic or ceramic parts and components duringheat-treatment processes, they are inserted into holding frames.Heat-treatment processes are, for example, sintering processes,hardening processes, finishing processes or soldering processes. Usualprocessing temperatures are between 700° C. and 2600° C., whereby onetypically works at between 800° C. and 1600° C.

According to the prior art, frames having such lattices comprise metal.The lattices are in that case formed by strands in the form of rodshaving e.g. a diameter of 2 mm. However, such holding devices exhibitconsiderable disadvantages which can be seen, inter alia, in thefollowing:

-   -   distortions during thermal cycles,    -   creep of the entire structure due to the effect of temperature,    -   high dead weight,    -   high heat capacity,    -   short life due to embrittlement,    -   high cost of adjustment to extend useful life,    -   increased waste of the parts to be treated due to distortion of        the holding device.

Due, particularly, to a reduced shape stability, problems are oftencaused in loading and unloading such holding devices by means ofmanipulators such as robots.

A fibrous composite part having a lattice-like structure which is usedin high-temperature furnaces and system construction, in heat-treatingtechnology or sintering technology as a lattice, is known from DE-A 19957 906. A fiber preform, which is produced especially according to TFP(Tailored Fiber Placement) technology and then pyrolyzed, i.e.carbonized or graphitized, is used for the production.

A carrier for hardening material is described in DE-U 295 12 569. Inthis case, the carrier comprises carbon fiber-reinforced carbon material(CFC material) which can have a protective layer consisting of SiC, BNor TiN. The carrier includes limbs that can be interconnected and haverecesses that are aligned with one another through which the material tobe hardened is passed.

A workpiece carrier for heat-treating workpieces is known from DE-A 19737 212. The workpiece carrier may comprise a one-piece monolithicallyformed frame on which bent rods can be placed which are used toaccommodate workpieces. According to a further embodiment, the carriercomprises a tubular construction about which the fiber bundles arewound, the fiber bundles extending at a spacing from one another.

The object of the present invention is to further develop a carrier, anda method for producing a carrier, of the aforementioned type in such away that a carrier is provided which is free of distortion, even understrong thermal loads or fluctuations in temperature, in order to be ableto subject components to a heat treatment to the desired extent.According to a further aspect, it should be ensured that contactreactions between the components to be treated and the carrier orlattice are avoided. It should be possible to produce the carrier orlattice itself with structurally simple steps.

According to the invention, the object is essentially solved by acarrier of the aforementioned type in that the frame comprisesheat-resistant material and the strands comprise carbon fibers orceramic fibers which, extending from the limb or limbs of the frame,form the lattice. In this case, in particular those strands consistingof fibers referred to as a fiber bundle, extend in a warp and woof-likeweb structure between the limbs or sections of the limbs of the frame.This produces a coarse web structure whose mesh size can be individuallypredetermined so as to accommodate components of any desired size.

If the frame consists of one limb, then that limb has a curved shape inorder to form e.g. an oval or a circle.

The carrier may consist of a single frame or of several frames,extending at a right angle or parallel to one another, which more orless combine to form a basket that is open on one side.

The lattice can be formed by single-layer or multilayer fiber strands(rovings) or intertwined rovings or intertwined fibers or yarns in theform of e.g. cords. Prefabricated mesh fabrics or a mesh-like structureproduced by means of TFP (Tailored Fiber Placement) are also possible.

In particular, when using fiber bundles, it is provided that the latticeis formed by a single, more or less endless fiber bundle extendingbetween the limbs of the frame.

Independently hereof, whether single-layer or multilayer fiber bundlesor intertwined fibers or yarns are used as fiber bundles, which consistof carbon fibers or ceramic fibers, according to one embodiment thelimbs of the frame have recesses on the longitudinal edges through whichsections of the fiber bundle pass for extending the mesh. In particular,the recesses themselves form a comb-like geometry in the respectivelongitudinal edge.

Alternatively, there is the possibility that the limbs are provided withopenings, such as borings, through which the fiber bundle passes.Depending on the position of the recesses or openings or their use, themesh spacing, i.e. the mesh width of the mesh netting, can be varied ina simple manner.

Furthermore, it is foreseen that the fiber bundle, laid out in the webstructure, is tensioned between the limbs, as a result of which it isensured that the finished lattice cannot sag, i.e. forms a plane.

In particular, Al₂O₃, SiC, BN, C or B₄C and/or combinations thereof arepossible as material for the rovings or fibers.

Preferably, the frame consists of CFC, graphite or fibrous ceramic. Theframe may have limbs produced by TFP (Tailored Fiber Placement)technology, which can be connected together by plug-in connections.However, there is also the possibility of cutting a frame, e.g. by meansof water jet, from a carbon fiber-reinforced carbon plate. Sections ofsuch a plate can also be assembled to form a frame.

As long as the carrier has a more or less two-dimensional geometry, i.e.consists of a single frame with a lattice extending from its limbs, eachlimb should preferably form a plane which extends at a right angle tothe plane formed by the lattice. If the limbs of the frame consist offlat elements, the flat sides thereof should consequently extend at aright angle to the lattice.

If the carrier has a basket geometry, i.e. e.g. a right parallelepipedthat is open on one side, the carrier consists of base and side frameswhich are each a holder for a lattice.

In this case, it is preferably provided that the upper limb of each sideframe is a flat element and/or the lower limb is an angular elementand/or each side limb extending at a right angle thereto is a roundelement.

Furthermore, the flat element formed as a limb should, with its flatside, form a plane in which or almost in which the lattice held by theframe extends.

Adjoining flat limbs, which abut at a right angle or almost at a rightangle, can be joined by a plug-in connection, which in turn extendwithin a round element. It is thereby provided that respective flatlimbs of the frame extend in a flush manner at their outer longitudinaledges into respective front ends of a round limb.

In particular, Al₂O₃ and/or SiC and/or BN and/or C or combinations ofone or more thereof are possible as fiber material.

Furthermore, a matrix can be provided for the woven structure which canconsist of the following materials and/or combinations thereof: carbon,B₄C, Al₂O₃, SiC, Si₃N₄ or mullite. The matrix can in that case beseparated from the gas phase by means of CVD and/or CVI or produced bypyrolysis of a precursor material such as phenol resin, furan resin orsilicon precursors. A combination of such process steps is alsopossible.

To exclude contact reactions between the parts to be thermally treatedand the carrier or lattice, a surface coating can, in addition, beapplied to the fibrous ceramic support structure. The surface coatingcan consist of oxides, nitrides and/or carbides of the 3rd and 4th maingroup and/or 3rd to 6th subgroup of the periodic system and/or carbon.

The bars of the finished lattice typically have a diameter of between 1mm and 10 mm, preferably between 2 mm and 4 mm.

The frame is preferably square or rectangular with a limb length of upto 2000 mm and/or a height of between 10 mm and 300 mm. Typicaldimensions can be:450×450×50 mm³ or900×600×40 mm³.

Other geometries of the frame, such as a circle or oval, are alsopossible. In this case, the frame can consist of e.g. a correspondinglycurved limb or of e.g. two limbs combining to form such a geometry.

According to the invention, a fibrous ceramic supporting structureconsisting of frame and lattice is provided with which metallic and/orceramic parts or components thereof can be positioned or fixed in aheat-treatment process. In particular due to the lattice structure, thepossibility is thereby given to vertically charge slim parts orcomponents to the desired extent. In addition, the mesh width of thelattice should be correspondingly predetermined. For this purpose, thelattice extends at a distance from the respective longitudinal edge ofeach limb of the frame.

By the teachings according to the invention, a distortion-free carrieris produced independently of any thermal cycles undertaken, so thatthere is no readjustment cost. The carrier according to the inventionexhibits a resistance to thermal shock, a low density and a lower heatcapacity. Also, a creep tendency is not produced. Furthermore, the factthat an embrittlement does not take place should be noted as a specialadvantage. A long life is also ensured. In comparison to metalliccarrier devices, a considerable reduction in waste is also observable.

A further advantage of the invention is the good flowability through thelattice structure. This results in great advantages when used in thehardening technology, e.g. during oil or gas quenching.

The previously described advantages relate not only to the carrier assuch, but also to its components, in particular the lattice, which canbe used as a separate part. Consequently, the invention also relates toa method for producing a lattice from intersecting strands of carbonfibers or ceramic fibers using a frame, from which the strands havingthe desired lattice structure are correspondingly extended, the matrixis then inserted into the fibers and subsequently the lattice is removedfrom the frame. The lattice can thereby be separated, e.g. severed, fromthe sections extending from the frame. The lattice can also be removedas a unit from the frame, if the strands extend from peripheralrecesses.

The matrix can be separated from the gas phase and/or formed bypyrolysis of a precursor material. Furthermore, the surface can becoated prior to removal of the lattice from the frame. Oxides, nitridesand/or carbides of the 3rd and 4th main group and/or 3rd to 6th subgroupof the periodic system and/or carbon or combinations of some of thesecan be used as materials for this purpose.

Al₂O₃, SiC, BN, C or combinations or partial combinations thereof arepossible as fiber material. Carbon, B₄C, Al₂O₃, SiC, Si₃N₄ or mullite orcombinations or partial combinations thereof can be used as material forthe matrix.

Such a lattice has a content of our own invention.

Further details, advantages and features of the invention are given notonly in the claims, the features found therein—alone and/or incombination—but also in the following description of a preferredembodiment illustrated in the drawings, in which:

FIG. 1 shows a first embodiment of a carrier,

FIG. 2 shows a second embodiment of a carrier,

FIG. 3 shows a first view of a third embodiment of a carrier, and

FIG. 4 shows a second view of the carrier according to FIG. 3.

FIGS. 1 and 2 show embodiments according to the invention of a more orless two-dimensional carrier, and FIGS. 3 and 4 of a three-dimensionalcarrier in the form of an open basket which has a parallelepipedgeometry.

A carrier 10, which is to be used as a fibrous ceramic supportingstructure, in particular, for positioning or fixing of e.g. metallic orceramic parts or components during heat-treatment processes, is shownpurely on principle in FIG. 1. The heat-treatment processes are e.g.sintering processes, hardening processes, finishing or solderingprocesses, which are carried out at temperatures of between 700° C. and2600° C., typically between 800° C. and 1600° C.

To ensure that the carrier 10 is distortion-free, independently of anythermal cycles that might occur, it comprises carbon fiber-reinforcedcarbon or a fibrous ceramic and includes a frame 11 with limbs 12, 14,16 18 as well as a lattice 20 extending or stretching therefrom. In theembodiment of FIG. 1, the lattice 20 is extended over projections 30,32, 34, 36 forming a comb-like structure of upper longitudinal edges 22,24, 26, 28 of the limbs 12, 14, 16, 18 and preferably consists of anendless carbon fiber strand. A ceramic fiber strand is also possible.

In particular, this is a single layer or multilayer fiber strand(roving).

The fiber strand forming the lattice 20 has, in particular, Al₂O₃, SiC,BN, C or combinations or partial combinations thereof as fiber-material.

The limbs 12, 14, 16, 18, which according to the embodiment shown inFIG. 2 can be joined together or otherwise connected, also consist ofCFC or ceramic material. It would also be possible to construct thelimbs as one piece, i.e. to form the frame integrally, by e.g. cuttingit out of a carbon fiber-reinforced carbon plate by means of e.g. awater jet.

If the lattice 20 has a matrix, it can be separated from the gas phase(e.g. CVD/CVI) or be formed by pyrolysis of a precursor material such ase.g. phenolic resin, furan resin or Si precursors.

Carbon, B₄C, Al₂O₃, SiC, Si₃N₄ or mullite or combinations or partialcombinations thereof are possible as materials for the matrix.

In addition, a surface coating can be provided which can compriseoxides, nitrides and/or carbides of the 3rd and 4th main group and/or3rd to 6th subgroup of the periodic system and/or carbon or combinationsor partial combinations thereof to prevent a contact reaction betweenthe holding structure and the parts to be thermally treated. Holdingstructure refers to the frame 11 and/or the lattice 20.

A carrier 38 shown in FIG. 2 also comprises a frame 40 with limbs 42,44, 46, 48 which are plugged together and between which a lattice 50 isextended. For this purpose, the limbs 42, 44, 46, 48 have bores 52, 54through which single-layer or multilayer fiber strands or intertwinedyarns pass which, in accordance with the aforementioned description, mayconsist of carbon fibers or ceramic fibers.

The carbon fibers, consisting especially of single-layer or multilayerfiber strands (rovings) or intertwined fiber strands (cords), forforming the lattice 20, 50 are laid to form a web structure, whereby thespacing between the strands can be preset to the desired degree independence on the projections 32, 34, 36, 30 extending from the limbs12, 14, 16, 18 or 42, 44, 46, 48 and utilized or bores 52, 54. Also, thestrands, i.e. in particular the fiber strands or yarns, forming thelattice 20, 50 are placed in a web structure (warp and woof).

A carrier 100 in the form of a basket can be seen in FIGS. 3 and 4which, in turn, consists of side frames 102, 104, 106, 108 and baseframe 110 and lattices 112, 114, 116, 118 and 120 stretching from them.Such a carrier 100 is intended, for example, for receiving metallic orceramic parts or components which are to be subjected to aheat-treatment process.

The side frames 102, 104, 106, 108 consist of upper flat elements 121,122, 124 and 125 and angular elements 126, 128, 130, 132 extending alongthe bottom which, in turn, form the base frame 110. Round elements 134,136, 138, 140 form the side limbs of the side frames 102, 104, 106, 108.

Furthermore, it can be seen in FIGS. 3 and 4 that the longitudinal limbs121, 122, 124, 125, 126, 128, 130, 132 are connected to one another byplug-in connections which extend into the round elements 134, 136, 138,140 and extend flush with one another at the outside, as illustrated inthe drawings.

The lattices 112, 114, 116, 118 are formed by single-layer or multilayerfiber strands, as can be seen in FIGS. 1 and 2. In this respect,reference is made to the embodiments relevant thereto.

The strands forming the lattice pass through bores, which are not shownin greater detail, in the limbs 121, 122, 124, 126 and the limb sections142, 144, 146, 148 of the angular elements 126, 128, 130 and 132. Thesections of the angular elements 126, 128, 130, 132 extending along thelattice 120 extend along the outer surface of the lattice 120 and thusserve as a support for the basket 100.

The lattices 112, 114, 116, 118, 120 or their fiber strands have, inparticular, Al₂O₃, SiC, BN, C or combinations or partial combinationsthereof as fiber material. If the respective lattice 112, 114, 116, 118,120 has a matrix, it can be separated from the gas phase (for exampleCVD/CVI) or be formed by pyrolysis of a precursor material such as e.g.phenolic resin, furan resin or Si precursors.

Carbon, B₄C, Al₂O₃, SiC, Si₃N₄ or mullite or combinations or partialcombinations thereof are possible as materials for the matrix.

Furthermore, a surface coating can be provided which can consist ofoxides, nitrides and/or carbides of the third and fourth main groupand/or the third to sixth subgroup of the periodic system and/or carbonor combinations or partial combinations thereof to prevent a contactreaction between the supporting structure and the parts to be thermallytreated.

The supporting structure refers to the respective frame 112, 114, 116,118, 120 and/or the lattice 102, 104, 106, 108, 110 stretching from it.

The limbs 121, 122, 124, 125, 126, 128, 130, 132, 134, 136, 138, 140 canconsist of CFC or ceramic material.

If the carrier 10, 38 or the basket 100 can be used for positioning orfixing a part to be subjected to a heat-treatment process, then it isalso possible to use the respective lattice 20, 50 itself. For thispurpose, it can be separated from the frame 11, 40. Thus, in theembodiment of FIG. 1, it is only necessary that the lattice 20 beremoved, i.e. pulled off, from the projections 30, 32, 34, 36. To usethe lattice 50 according to FIG. 2, the sections passing through thebores 42, 54 must be removed.

Furthermore, it should be noted that the carbon fiber-reinforced carbonbody, whether it be the lattice or the frame, can be converted intoC—SiC or C/C—SiC by siliconization by means of an e.g. capillaryinfiltration process or liquid infiltration process with liquid silicon.

1. A carrier (10, 38, 100) for structural parts to be subjected to aheat-treatment process, including at least one frame (11, 40, 102, 104,106, 108, 110) and a lattice (20, 50, 112, 114, 116, 118, 120)comprising intersecting strands extending therefrom, wherein the frameconsists of one or more limbs (12, 14, 16, 18, 42, 44, 46, 48, 121, 122,124, 125, 126, 128, 130, 132, 134, 136, 138, 140) preferably forming apolygon, characterized in that the frame (11, 40, 102, 104, 106, 108,100) comprises temperature-resistant material and the strands which formthe lattice (20, 50, 112, 114, 116, 118, 120) extending from the limb orlimbs (12, 14, 18, 42, 44, 46, 48, 121, 122, 124, 125, 126, 128, 130,132, 134, 136, 138, 140) of the frame comprises carbon fibers or ceramicfibers.
 2. The carrier according to claim 1, characterized in that thecarrier (100) comprises a plurality of frames (102, 104, 106, 108, 100)forming a three-dimensional body.
 3. The carrier according to claim 2,characterized in that the three-dimensional body has a basket geometry.4. The carrier according to claim 1, characterized in that the carbonfiber-reinforced carbon material or ceramic material forming the lattice(20, 50) is a fiber bundle in the form of single-layer or multilayerfiber strands or intertwined yarns and that the fiber bundle extends ina warp and woof web structure between the limbs (12, 14, 16, 18, 42, 44,46, 48) of the frame.
 5. The carrier according to at least claim 1 orclaim 4, characterized in that the lattice (20, 50) is formed by asection of an endless fiber bundle extending between the limbs (12, 14,16, 18, 42, 44, 46, 48) of the frame.
 6. The carrier according to atleast claim 1, characterized in that the limbs (12, 14, 16, 18) have, intheir respective longitudinal edges, recesses through which extendsections of the fiber bundle for extending the lattice (20, 50).
 7. Thecarrier according to claim 6, characterized in that the recesses form acomb-like geometry in the respective longitudinal edge (24, 26, 28, 30)of the frame limb (12, 14, 16, 18).
 8. The carrier according to at leastclaim 1, characterized in that the limbs (42, 44, 46, 48) of the frame(40) have openings, such as borings (52, 54), through which the fiberbundle passes.
 9. The carrier according to at least claim 4,characterized in that the fiber bundle, laid in the web structure,extends under tension between the limbs (12, 14, 16, 18, 42, 44, 46,48).
 10. The carrier according to at least claim 1, characterized inthat the frame (11, 52) is integrally cut out of a carbonfiber-reinforced carbon plate.
 11. The carrier according to at leastclaim 1, characterized in that the limbs (42, 44, 46, 48) forming theframe (40) are joined together by means of plug-in connections.
 12. Thecarrier according to at least claim 1, characterized in that the base ofthe frame (11, 38) or its limbs (12, 14, 16, 18, 42, 44, 46, 48) is apyrolyzed fiber preform produced by means of TFP technology.
 13. Thecarrier according to at least claim 1, characterized in that the frame(11, 40) consists of a section or sections severed, in particular bymeans of water jet cutting, from a carbon fiber-reinforced carbon plate,such as a CFC plate.
 14. The carrier according to at least claim 1,characterized in that the lattice (20, 50) is produced by means of a TFPmethod.
 15. The carrier according to at least claim 1, characterized inthat the fiber material consists of or contains Al₂O₃ and/or SiC and/orBN and/or C.
 16. The carrier according to at least claim 1,characterized in that the lattice (20, 50) has a matrix which consistsof or contains carbon, B₄C, Al₂O₃, SiC, Si₃N₄ and/or mullite.
 17. Thecarrier according to claim 16, characterized in that the matrix isseparated from the gas phase and/or formed by pyrolysis of a precursormaterial.
 18. The carrier according to claim 17, characterized in thatthe precursor material is phenolic resin and/or furan resin and/or a Siprecursor.
 19. The carrier according to at least claim 1, characterizedin that at least the lattice has a coating of, or contains, oxides,nitrides and/or carbides of the third and fourth main group and/or thethird to sixth subgroup of the periodic system and/or carbon.
 20. Thecarrier according to at least claim 1, characterized in that the frame(11, 40) consists of carbon fiber-reinforced carbon, fiber ceramic orgraphite.
 21. The carrier according to at least claim 1, characterizedin that the carrier (100) has a parallelepiped geometry open on one sidewith bottom and side frames (102, 104, 106, 108, 110) which are eachholders for a lattice (112, 114, 116, 118, 120).
 22. The carrieraccording to at least claim 21, characterized in that the upper limb(121, 122, 124, 125) of each side frame (112, 114, 116, 118) is a flatelement and/or the lower limb (126, 128, 130, 132) of each side frame isan angular element and/or the side limbs (134, 136, 138, 140) extendingat a right angle thereto are each a round element.
 23. The carrieraccording to at least claim 22, characterized in that the flat elementforms, with its flat side, a plane in which, or approximately in which,extends the lattice (112, 114, 116, 118) stretched out by the frame(102, 104, 106, 108) extends.
 24. The carrier according to at leastclaim 22, characterized in that the respective flat element (121, 122,124, 125) of the side frame (112, 114, 116, 118), at the outerlongitudinal edge side, extends in a flush manner into the respectivefront end of a round element (134, 136, 138, 140).
 25. The carrieraccording to at least claim 22, characterized in that adjoining flatelements of frames (102, 104, 106, 108) abutting one another at a rightangle, or approximately at a right angle, are connected by a plug-inconnection which, in turn, extends into one of the round elements (134,136, 138, 140).
 26. A method for producing a component consisting ofintersecting strands of carbon fibers or ceramic fibers using a framecomposed of one or more limbs, from which the strands having the desiredlattice structure are correspondingly extended, a matrix is theninserted into the fibers and the lattice is subsequently removed fromthe frame.
 27. The method according to claim 26, characterized in thatthe lattice is separated, e.g. severed, from its sections extending fromthe frame.
 28. The method according to claim 26, characterized in thatthe matrix is separated from the gas phase and/or formed by pyrolysis ofone or more precursor materials.
 29. The method according to claim 27,characterized in that the lattice is surface-coated prior to and/orafter removal of the lattice from the frame.
 30. The method according toat least claim 26, characterized in that Al₂O₃ and/or SiC and/or BNand/or C is used as the fibers or fiber material.
 31. The methodaccording to at least claim 26, characterized in that carbon and/or B₄Cand/or Al₂O₃ and/or SiC and/or Si₃N₄ and/or mullite is used as matrixmaterial.
 32. The method according to at least claim 26, characterizedin that the lattice is surface-coated with oxides, nitrides and/orcarbides of the third and fourth main group and/or the third to sixthsubgroup of the periodic system and/or carbon.
 33. A lattice or methodfor producing a lattice according to one of the claims 1 to 32.